Jake, it looks like you are missing (or overwrote) your /includes/config.inc.php file with the stock one.

The error message means that its looking for a file specified at a configured directory listed within that /includes/config.inc.php file.

If you happened to accidentally overwrite your forum's config.inc.php file, you can either; A) rename and use the config-bak.inc.php file that UBB.threads.7.6.2 created within that same /includes directory. or B) restore an earlier version of your config.inc.php from the backup you did just before performing your upgrade.

Well, the upgrade steps have you exclude several files and folders for an upgrade which contain your unique configuration; the includes folder for example has all of your board rules, config, coppa, header, footer, forum introductions, sharaholic information, privacy policy, etc. If you overwrote them you'll want to restore the folders you should generally exclude from an upgrade.

A new install comes with several files which will overwrite the includes folder if the upgrade instructions aren't followed; these files in the 7.7.0 release are:cache_builders/custom/*includes/boardrules.phpincludes/closedforums.phpincludes/community_intro.phpincludes/config.inc.phpincludes/coppainsert.phpincludes/footer.phpincludes/header.phpincludes/header-insert.phpincludes/privacy.phpstyles/wrappers.php

At this point, I don't know what happened. I know the instructions don't list the includes directory. But those files were not there after the upgrade. Probably something I did inadvertently, but I have no idea what.

Am I ok with using these files from backup in the /includes directory? They are from my backup before I installed 7.6.2.